Paul Lewis | 911c1b8 | 2019-12-02 12:46:15 | [diff] [blame] | 1 | If you want to write an option parser, and have it be good, there are |
| 2 | two ways to do it. The Right Way, and the Wrong Way. |
| 3 | |
| 4 | The Wrong Way is to sit down and write an option parser. We've all done |
| 5 | that. |
| 6 | |
| 7 | The Right Way is to write some complex configurable program with so many |
| 8 | options that you hit the limit of your frustration just trying to |
| 9 | manage them all, and defer it with duct-tape solutions until you see |
| 10 | exactly to the core of the problem, and finally snap and write an |
| 11 | awesome option parser. |
| 12 | |
| 13 | If you want to write an option parser, don't write an option parser. |
| 14 | Write a package manager, or a source control system, or a service |
| 15 | restarter, or an operating system. You probably won't end up with a |
| 16 | good one of those, but if you don't give up, and you are relentless and |
| 17 | diligent enough in your procrastination, you may just end up with a very |
| 18 | nice option parser. |
| 19 | |
| 20 | ## USAGE |
| 21 | |
| 22 | ```javascript |
| 23 | // my-program.js |
| 24 | var nopt = require("nopt") |
| 25 | , Stream = require("stream").Stream |
| 26 | , path = require("path") |
| 27 | , knownOpts = { "foo" : [String, null] |
| 28 | , "bar" : [Stream, Number] |
| 29 | , "baz" : path |
| 30 | , "bloo" : [ "big", "medium", "small" ] |
| 31 | , "flag" : Boolean |
| 32 | , "pick" : Boolean |
| 33 | , "many1" : [String, Array] |
| 34 | , "many2" : [path, Array] |
| 35 | } |
| 36 | , shortHands = { "foofoo" : ["--foo", "Mr. Foo"] |
| 37 | , "b7" : ["--bar", "7"] |
| 38 | , "m" : ["--bloo", "medium"] |
| 39 | , "p" : ["--pick"] |
| 40 | , "f" : ["--flag"] |
| 41 | } |
| 42 | // everything is optional. |
| 43 | // knownOpts and shorthands default to {} |
| 44 | // arg list defaults to process.argv |
| 45 | // slice defaults to 2 |
| 46 | , parsed = nopt(knownOpts, shortHands, process.argv, 2) |
| 47 | console.log(parsed) |
| 48 | ``` |
| 49 | |
| 50 | This would give you support for any of the following: |
| 51 | |
| 52 | ```console |
| 53 | $ node my-program.js --foo "blerp" --no-flag |
| 54 | { "foo" : "blerp", "flag" : false } |
| 55 | |
| 56 | $ node my-program.js ---bar 7 --foo "Mr. Hand" --flag |
| 57 | { bar: 7, foo: "Mr. Hand", flag: true } |
| 58 | |
| 59 | $ node my-program.js --foo "blerp" -f -----p |
| 60 | { foo: "blerp", flag: true, pick: true } |
| 61 | |
| 62 | $ node my-program.js -fp --foofoo |
| 63 | { foo: "Mr. Foo", flag: true, pick: true } |
| 64 | |
| 65 | $ node my-program.js --foofoo -- -fp # -- stops the flag parsing. |
| 66 | { foo: "Mr. Foo", argv: { remain: ["-fp"] } } |
| 67 | |
| 68 | $ node my-program.js --blatzk -fp # unknown opts are ok. |
| 69 | { blatzk: true, flag: true, pick: true } |
| 70 | |
| 71 | $ node my-program.js --blatzk=1000 -fp # but you need to use = if they have a value |
| 72 | { blatzk: 1000, flag: true, pick: true } |
| 73 | |
| 74 | $ node my-program.js --no-blatzk -fp # unless they start with "no-" |
| 75 | { blatzk: false, flag: true, pick: true } |
| 76 | |
| 77 | $ node my-program.js --baz b/a/z # known paths are resolved. |
| 78 | { baz: "/Users/isaacs/b/a/z" } |
| 79 | |
| 80 | # if Array is one of the types, then it can take many |
| 81 | # values, and will always be an array. The other types provided |
| 82 | # specify what types are allowed in the list. |
| 83 | |
| 84 | $ node my-program.js --many1 5 --many1 null --many1 foo |
| 85 | { many1: ["5", "null", "foo"] } |
| 86 | |
| 87 | $ node my-program.js --many2 foo --many2 bar |
| 88 | { many2: ["/path/to/foo", "path/to/bar"] } |
| 89 | ``` |
| 90 | |
| 91 | Read the tests at the bottom of `lib/nopt.js` for more examples of |
| 92 | what this puppy can do. |
| 93 | |
| 94 | ## Types |
| 95 | |
| 96 | The following types are supported, and defined on `nopt.typeDefs` |
| 97 | |
| 98 | * String: A normal string. No parsing is done. |
| 99 | * path: A file system path. Gets resolved against cwd if not absolute. |
| 100 | * url: A url. If it doesn't parse, it isn't accepted. |
| 101 | * Number: Must be numeric. |
| 102 | * Date: Must parse as a date. If it does, and `Date` is one of the options, |
| 103 | then it will return a Date object, not a string. |
| 104 | * Boolean: Must be either `true` or `false`. If an option is a boolean, |
| 105 | then it does not need a value, and its presence will imply `true` as |
| 106 | the value. To negate boolean flags, do `--no-whatever` or `--whatever |
| 107 | false` |
| 108 | * NaN: Means that the option is strictly not allowed. Any value will |
| 109 | fail. |
| 110 | * Stream: An object matching the "Stream" class in node. Valuable |
| 111 | for use when validating programmatically. (npm uses this to let you |
| 112 | supply any WriteStream on the `outfd` and `logfd` config options.) |
| 113 | * Array: If `Array` is specified as one of the types, then the value |
| 114 | will be parsed as a list of options. This means that multiple values |
| 115 | can be specified, and that the value will always be an array. |
| 116 | |
| 117 | If a type is an array of values not on this list, then those are |
| 118 | considered valid values. For instance, in the example above, the |
| 119 | `--bloo` option can only be one of `"big"`, `"medium"`, or `"small"`, |
| 120 | and any other value will be rejected. |
| 121 | |
| 122 | When parsing unknown fields, `"true"`, `"false"`, and `"null"` will be |
| 123 | interpreted as their JavaScript equivalents. |
| 124 | |
| 125 | You can also mix types and values, or multiple types, in a list. For |
| 126 | instance `{ blah: [Number, null] }` would allow a value to be set to |
| 127 | either a Number or null. When types are ordered, this implies a |
| 128 | preference, and the first type that can be used to properly interpret |
| 129 | the value will be used. |
| 130 | |
| 131 | To define a new type, add it to `nopt.typeDefs`. Each item in that |
| 132 | hash is an object with a `type` member and a `validate` method. The |
| 133 | `type` member is an object that matches what goes in the type list. The |
| 134 | `validate` method is a function that gets called with `validate(data, |
| 135 | key, val)`. Validate methods should assign `data[key]` to the valid |
| 136 | value of `val` if it can be handled properly, or return boolean |
| 137 | `false` if it cannot. |
| 138 | |
| 139 | You can also call `nopt.clean(data, types, typeDefs)` to clean up a |
| 140 | config object and remove its invalid properties. |
| 141 | |
| 142 | ## Error Handling |
| 143 | |
| 144 | By default, nopt outputs a warning to standard error when invalid values for |
| 145 | known options are found. You can change this behavior by assigning a method |
| 146 | to `nopt.invalidHandler`. This method will be called with |
| 147 | the offending `nopt.invalidHandler(key, val, types)`. |
| 148 | |
| 149 | If no `nopt.invalidHandler` is assigned, then it will console.error |
| 150 | its whining. If it is assigned to boolean `false` then the warning is |
| 151 | suppressed. |
| 152 | |
| 153 | ## Abbreviations |
| 154 | |
| 155 | Yes, they are supported. If you define options like this: |
| 156 | |
| 157 | ```javascript |
| 158 | { "foolhardyelephants" : Boolean |
| 159 | , "pileofmonkeys" : Boolean } |
| 160 | ``` |
| 161 | |
| 162 | Then this will work: |
| 163 | |
| 164 | ```bash |
| 165 | node program.js --foolhar --pil |
| 166 | node program.js --no-f --pileofmon |
| 167 | # etc. |
| 168 | ``` |
| 169 | |
| 170 | ## Shorthands |
| 171 | |
| 172 | Shorthands are a hash of shorter option names to a snippet of args that |
| 173 | they expand to. |
| 174 | |
| 175 | If multiple one-character shorthands are all combined, and the |
| 176 | combination does not unambiguously match any other option or shorthand, |
| 177 | then they will be broken up into their constituent parts. For example: |
| 178 | |
| 179 | ```json |
| 180 | { "s" : ["--loglevel", "silent"] |
| 181 | , "g" : "--global" |
| 182 | , "f" : "--force" |
| 183 | , "p" : "--parseable" |
| 184 | , "l" : "--long" |
| 185 | } |
| 186 | ``` |
| 187 | |
| 188 | ```bash |
| 189 | npm ls -sgflp |
| 190 | # just like doing this: |
| 191 | npm ls --loglevel silent --global --force --long --parseable |
| 192 | ``` |
| 193 | |
| 194 | ## The Rest of the args |
| 195 | |
| 196 | The config object returned by nopt is given a special member called |
| 197 | `argv`, which is an object with the following fields: |
| 198 | |
| 199 | * `remain`: The remaining args after all the parsing has occurred. |
| 200 | * `original`: The args as they originally appeared. |
| 201 | * `cooked`: The args after flags and shorthands are expanded. |
| 202 | |
| 203 | ## Slicing |
| 204 | |
| 205 | Node programs are called with more or less the exact argv as it appears |
| 206 | in C land, after the v8 and node-specific options have been plucked off. |
| 207 | As such, `argv[0]` is always `node` and `argv[1]` is always the |
| 208 | JavaScript program being run. |
| 209 | |
| 210 | That's usually not very useful to you. So they're sliced off by |
| 211 | default. If you want them, then you can pass in `0` as the last |
| 212 | argument, or any other number that you'd like to slice off the start of |
| 213 | the list. |